Missing validation for data from D-Bus

[joseivanlopez]

The D-Bus API provided by D-Installer uses variant type for some values. For example, when calling to calculate a new storage proposal:

$ busctl call \
    org.opensuse.DInstaller.Storage \
    /org/opensuse/DInstaller/Storage/Proposal1 \
    org.opensuse.DInstaller.Storage.Proposal1 \
    Calculate \
    a{sv} 1 CandidateDevices as 1 /dev/vdc

There is no validation from backend size about the types sent, so it could fail if it receives an unexpected value:

$ busctl call \
    org.opensuse.DInstaller.Storage \
    /org/opensuse/DInstaller/Storage/Proposal1 \
    org.opensuse.DInstaller.Storage.Proposal1 \
    Calculate \
    a{sv} 1 CandidateDevices au 1 1000

The backend should verify the data received from D-Bus.

[mvidner]

From the perspective of the D-Bus protocol and the ruby-dbus bindings library, this is out of scope: a Calculate method is getting an a{sv} argument and D-Bus has no other information to help in the validation. So it is the application's responsibility.

That said, there's an example from NM and a related bug in ruby-dbus:

Just for reference, we've recently seen how NetworkManager handles this kind of errors, in mvidner/ruby-dbus#124:

connection.permissions: wrong type; should be a list of strings. error_name=org.freedesktop.NetworkManager.Settings.Connection.InvalidProperty (DBus::Error)

ipv4.address-data: can't set property of type 'aa{sv}' from value of type 'av' error_name=org.freedesktop.NetworkManager.Settings.Connection.InvalidProperty (DBus::Error)

Even when ruby-dbus has the type information, for properties, it still fails to check the types. That's part of mvidner/ruby-dbus#118. Example:

$ sudo busctl --system \
  call \
  org.opensuse.DInstaller.Questions \
  /org/opensuse/DInstaller/Questions1 \
  org.opensuse.DInstaller.Questions1 \
  New sasas "should I stay or should I go" 2 yes no 1 yes
$ sudo busctl --system \
  set-property \
  org.opensuse.DInstaller.Questions \
  /org/opensuse/DInstaller/Questions1/1 \
  org.opensuse.DInstaller.Question1 \
  Answer i 13
Failed to set property Answer on interface org.opensuse.DInstaller.Question1: undefined method `to_sym' for 13:Integer
            backend.answer = option.to_sym

The exception comes from a random place in the method body, not from a typechecking guard.

So when I add the missing type checks, I'll keep in mind an option to let the methods be usable by applications for "custom properties".

[ancorgs]

Now that we have switched from D-Bus to HTTP as main communication protocol, I closing this. I know D-Bus is still used internally at some parts, but this is likely not worth any investment.

Feel free to reopen if you disagree.